Increase gdb exit timeout to avoid halting the target on exit

Increase gdb exit timeout. Before it was too strict and caused a force kill of the gdb server, which could leave the target in a halted state on exit.

This is an unofficial release (forked repo). Opened an issue Marus#1122

To install:

1. download the .vsix release file
2. go to the extensions tab in VSCode --> ... --> "Install From VSIX" (or find it from the command panel)
3. choose the vsix file
4. restart extensions